(HealthDay News) – The natural course of unruptured cerebral aneurysms varies according to their size, location, and shape.

Akio Morita, MD, PhD, from the NTT Medical Center Tokyo, and colleagues analyzed data on 5,720 patients (mean age, 62.5 years; 68% women) with newly identified, saccular aneurysms that were >3mm in the largest dimension.

The researchers found that 91% of the 6,697 aneurysms were discovered incidentally. Most aneurysms were in the middle cerebral arteries (36%) and the internal carotid arteries (34%), with a mean size of 5.7 ± 3.6mm. During follow-up, 111 patients had documented ruptures (annual rate of rupture, 0.95%), with the risk of rupture increasing with the increasing size of the aneurysm. With aneurysms that were 3–4mm in size as the reference, the hazard ratios for rupture with increasing size were as follows: 5–6 mm, 1.13 (95% confidence interval [CI], 0.58–2.22); 7–9 mm, 3.35 (95% CI, 1.87–6); 10–24mm, 9.09 (95%CI, 5.25–15.74); and >25mm, 76.26 (95% CI, 32.76–177.54). Also more likely to rupture were aneurysms with an irregular protrusion of the wall of the aneurysm (hazard ratio, 1.63; 95% CI, 1.08–2.48).

“This study showed that the natural course of unruptured cerebral aneurysms varies according to the size, location, and shape of the aneurysm,” the authors write.

One author disclosed financial ties to the biopharmaceutical and medical equipment industries.

Full Text (subscription or payment may be required)